Rail fasteners

ABSTRACT

A rail to tie fastening including an elastic clip (12) a clip holder (15) and a locking element (6). The locking element (6) being interposed between the foot of the rail (11) and the clip holder (15) and, between the foot of the rail (11) and the clip (12) and is forced by the clip (12) against the foot (11). The locking element (6) is so shaped that any movement of the locking element (6) parallel to the rail (11), induced by longitudinal movement of the rail (11), results in the locking element (6) wedging between the clip holder (15) and the foot of the rail (11) so increasing lateral pressure on the rail to prevent further longitudinal rail movement.

This invention relates to an improvement in elastic rail fastenersparticularly those which use a rail clip and a clip holder. The purposeof the clip holder is to secure the rail clip to a rail sleeper andenables the rail clip to bear down on the rail flange.

Numerous elastic rail fastening systems of this type have been devised.Any rail fastening system must be able to maintain the rail in positionunder the normal stress conditions arising from use of the rails andfrom environmental stresses particularly thermal stresses. Modern railsystems are adopting welded rails and thermal stresses are a predominantfactor in welded rails. It has been observed that a major long termdifficulty with rails is the tendency of the rails to move in thepredominant direction of travel for trains on the rail track. Thistendency is called rail creep and it is most important that any elasticrail fastening systems not only prevent lateral rail movement but alsoprevent axial movement or rail creep.

Past attempts to reduce rail creep have concentrated on increasing thehold down force of the rail clip on the rail flange or on increasing thefrictional resistance between the rail, the sleeper and the clip by, forexample, carefully selecting material to be used as rail pads betweenthe rail and the sleeper.

It is an object of this invention to reduce rail creep as compared toconventional elastic fastening systems.

To this end the present invention provides a locking element for usewith a rail fastening system comprising an elastic rail clip, a clipholder adapted to hold the clip in position on the flange of the rail.The locking element is adapted to lie between the rail flange and therail clip holder, and the locking element is held down onto the railflange by the rail clip, and the clip holder interfits with the lockingelement such that any movement of the locking element in a directionparallel to the rail axis is at least partially translated into alateral pressure of the locking element against the rail.

Ideally a portion of the abutting surfaces of the locking element andthe clip holder are inclined to the axis of the rail so that anymovement of the locking element parallel to the rail results in thelocking element being wedged inwardly against the rail, therebyincreasing contact pressure on the rail from a horizontal lateraldirection. Prior art fastening systems only applied a vertical hold downforce to the rail flange. The present invention however is able to applyboth a vertical and horizontal force to the rail and this additionallyrestrains rail creep. Either locking element or the clipholder includesa U shaped recess into which the other part interfits and either thecorners of said U have a radius of curvature of at least 6 mm or thesides of said U are inclined to the base of said U at an angle of atleast 100°.

The locking element of this invention ideally doubles as an insulatorbetween the rail clip and the rail flange. In the prior art insulatorsof this kind have been described for example in U.S. Pat. Nos. 3,610,526to Burwell (see FIG. 4), 3,460,756 to Sanson, 3,463,394 to Jones et al.None of the insulators described in these patents or insulators used inpractice in the prior art functioned as locking elements. Theinteraction of the surface of the insulator against the clip holder inthe prior art did not result in longitudinal movement of the insulatorbeing translated into lateral pressure on the edge of the rail foot. Ineach of the prior art insulators, the insulators and their associatedrail clip holders are not shaped to provide a wedge like interfitting.Rather the angles at the corners of the rail clip holders and internalcorners of the insulators adjacent the clip holders are effectivelyright angles.

From the above it can be seen that the locking element of the inventionmust be shaped to lie on top of the rail flange and on the shoulder orside of the rail flange so that it lies between the rail clip and thetop surface of the rail flange and lies between the clip holder and theside of the rail flange. Preferably the locking element includes a Ushaped portion which surrounds the clip holder. The internal faces ofthe U portion, which abut the rail clip are either curved or inclinedinwardly toward the rail ensuring that longitudinal movement istranslated into the lateral direction toward the rail. It is preferredto select the material for the locking element on two criteria: strengthand frictional resistance of the surface. Both metal or a reinforcedplastic are considered to be suitable.

The rail clip and clipholder preferred for use with the locking elementof this invention are described in Australian patent application54004/79.

A preferred embodiment of this invention will now be described inrelation to FIGS. 1 to 4 of the drawings.

FIG. 1 is a pictorial view of the locking element.

FIG. 2 is a plan view of the locking element.

FIG. 3 is a sectional view taken about on line 3--3 in FIG. 2.

FIG. 4 is a sectional view of a rail fastening system incorporating thelocking element, and

FIG. 5 is a plan view of the system shown in FIG. 4 and taken about online 5--5 in FIG. 4.

The locking element 6 includes a portion 7 which lies on the rail flangeand two shoulders 8 which encompass the clip holder. The element furthercomprises an outer rim 9 and the shoulders include in their leading edgethe inclined wedging surface 21.

As shown in FIGS. 3 and 4 the rail fastening system comprises a rail 10with a rail flange 11, a rail clip 12 secured in clip holder 15. Therail clip comprises a base portion 13 and spring portion 14 which seatson the locking element portion 7 and effectively holds down the railflange. The clip holder is formed from pressed metal plate and hasrounded shoulders 16 which seat within the shoulders 8 of lockingelement 6. In particular, the rail clip 12 is an elastic, U-shapedmember having base 13 and two arms extending therefrom providing thespring portion 14. The base 13 is adapted to be secured by clip holder15 to the tie outwardly spaced from the foot of rail 10. The arms ofspring portion 14 are bent inwardly beyond base 13 and oriented forcontact with the flange of rail 10 such that the arms are deflectedupwardly relative to rail 10 to develop downward clamping forces tendingto hold rail 10 on the tie. Preferably each arm of spring portion 14 istapered and this tapering is preferably substantially uniformly over theentire length of each arm. Clip holder 15 is adapted to be secured tothe rail tie and has a general U shaped body portion with the sides ofthe U being slotted toward the base of the U and the slots adapted toreceive the base 13 of clip 12. The U cross section of clip holder 15 isin the horizontal plane and the slots are generally horizontal. Thesides of the U slope inwardly to guide clip 12 into position and toenable insertion of the clip base 13 into the slots.

Any rail creep will tend to drag the locking element past the clipholder but the wedging action of the surface 21 of shoulders 8 of thelocking element 6 and shoulders 16 of the clip holder 15 will increasethe lateral hold of the locking elements on the rail flange.

In this embodiment the rail is electrified and the locking element 6doubles as an insulator and is accordingly composed of glass fillednylon. To improve the friction properties of the locking element theface of the locking element which abuts the rail may be roughened ortextured either by sandblasting or other suitable means.

A comparison test was carried out with an insulator which did notproduce a lateral wedging action by dragging a rail through the railseat past the clipholder and measuring the resistance force. Then thetest was repeated with an identical insulator except that a lateralwedging action was produced according to this invention. These testswere repeated several times.

In each case there was a significant increase in the force required toachieve significant rail creep when the locking element of thisinvention was used. Significant rail creep is considered to occur withrail movement of from 3 to 6 mm. The smallest increase in rail creepresistance force between using a locking element which created nowedging action and the locking element of this invention was 79% whilethe largest difference was 110%.

The locking element insulator 6 is a key element in preventing railcreep (i.e. longitudinal movement of the rail). As well because it is aseparate part from the clip holder and is subject to more stress it canbe easily and inexpensively replaced without replacement of the clipholder which is not the case in some prior art systems where clipholders encapsulated in insulating plastic have been used.

Thus the present invention clearly provides a marked improvement overprior art fastening systems without the need of increasing the hold downforce capacity of the rail clip. Moreover, the increased cost in makingfastening systems of the present invention is small or negligible whereinsulators are required in any case.

We claim:
 1. A rail fastening system comprising an elastic rail clip, a clip holder adapted to hold the clip in position on the flange of the rail and a locking element being adapted to lie between the rail flange, the rail clip and the clip holder, said rail having a longitudinal axis, said locking element being held down onto the rail flange by the rail clip to apply a generally vertical holding force to the rail and said clip holder interfitting with said locking element such that any movement of said locking element induced by the rail in a direction parallel to the rail longitudinal axis is at least partially translated into a lateral pressure of said locking element against said rail in an amount sufficient to apply a generally horizontal holding force to the rail, said vertical and horizontal forces serving to retard longitudinal movement of the rail, said clipholder having an external face complementary in shape with said locking element to provide a wedge-like interfitting, the complementary shape being in the form of a U wherein the corners of the U have a radius of curvature sufficient to provide a wedging action which translates said movement of said locking element into said lateral pressure and where each side of the U is inclined at an angle to the base of the U sufficient to provide a wedging action which translates movement of said locking element into said lateral pressure.
 2. A system as claimed in claim 1 wherein said locking element includes a U shaped portion which fits about the rail clip holder and the corners of said U portion have a radius of curvature sufficient to provide a wedging action which translates said movement of said locking element into said lateral pressure.
 3. A system as claimed in claim 1 wherein said locking element includes a U shaped portion which fits about the rail clip holder and each side of said U portion is inclined at an angle to the base of said U portion sufficient to provide a wedging action which translates said movement of said locking element into said lateral pressure.
 4. A system as claimed in claim 1 in which the locking element fits within a U shaped recess of said clip holder and the radius of curvature of the corners of said U shaped recess is sufficient to provide a wedging action which translates said movement of said locking element into said lateral pressure.
 5. A system as claimed in claim 1 wherein the locking element fits within a U shaped recess of said rail clip holder and each side of said U shaped recess is inclined at an angle to the base of said U shaped recess sufficient to provide a wedging action which translates said movement of said locking element into said lateral pressure. 